JPH07283451A - Laminated piezoelectric element - Google Patents

Abstract

PURPOSE:To provide a laminated piezoelectric element capable of avoiding the release and the defective bonding caused in the cutting and driving steps of the conductive projections of the element by forming the conductive projections having excellent electrochemical bonding strength in a stable shape. CONSTITUTION:A conductive projections 16 electrically connecting to a copper foil 16 to be an outer electrode are formed on the end of every other layer of inner electrodes 12 exposed to the element side. These conductive projections 16 are composed of conductive pasty layers 16a and electroplating layers 16b provided on the conductive pasty layers 16a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element in which a plurality of thin films of piezoelectric material are laminated and a longitudinal displacement can be obtained by applying a voltage.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a laminated piezoelectric element,
A general method is to print electrodes on the entire surface of the piezoelectric sheet and stack the electrodes. In the case of such a structure, it is necessary to electrically connect every other internal electrode. As an example thereof, a method as shown in FIGS. 9 and 10 is considered.

First, as shown in FIG. 9 (a), a film-shaped piezoelectric material 71 on which an internal electrode 72 is printed is laminated every other layer so that the end portion of the internal electrode 72 is exposed, and then sintered. The sintered body 70 is formed. Then, temporary external electrodes 73 and 74 are applied to the side surfaces where the end portions of the internal electrodes 72 are exposed every other layer, and electroplating is performed using the temporary external electrodes 73 as a cathode. As shown, the conductive protrusions 75 formed by the electroplating method are formed in alternate layers.

The sintered body 70 will be described below with reference to a vertical sectional view.
As shown in FIG. 10C, the resin component 76 is electrodeposited on the ends of the conductive protrusions 75 and the internal electrodes 72 by an electrodeposition coating method or the like, and baked at around 150 ° C. As shown, the resin component is melted to form the insulating layer 77.

On the other hand, as shown in FIG. 10 (e), thermocompression bonding is possible, and only the pressing portion has conductivity in one direction,
An anisotropic conductive film 78 containing conductive particles 80 and a copper foil 79 which will be an external electrode are attached to each other.
As shown in 0 (f), the anisotropic conductive film 7 is formed by thermocompression bonding.
In the case of No. 8, only the portion facing the conductive convex portion 75 is partially pressurized with a higher pressure than the other portions, and as a result,
The conductive particles 80 in the portion pressed by the high pressure are the insulating layers 7.
7 and the conductive protrusions 75 and the copper foil 79 are brought into contact with each other, and the copper foil 79 and the conductive protrusions 75 to be external electrodes are formed.
And the internal electrodes 72 are electrically connected every other layer.

[0006] In the same manner, the sintered body 70 in which the internal electrodes and the copper foil, which are one layer apart, are connected by shifting the layers on the opposite side surface,
Is a finished product after undergoing steps such as lead wire attachment, resin coating, and polarization treatment.

[0007]

However, in the manufacturing process of the laminated piezoelectric element as described above, the conductive convex portion 75 is formed on the end portion of the internal electrode 72 having a width of 5 to 10 μm by the electroplating method. Therefore, due to the nature of the electroplating method, it is formed with a width much wider than the width of the internal electrodes. As a result, depending on the degree of exposure of the end of the internal electrode 72 and the extent of expansion of the conductive convex portion 75, the conductive convex portion 75 may contact the internal electrodes 72 adjacent on both sides to electrically short-circuit, Alternatively, since the heights of the conductive protrusions 75 are likely to be uneven, there is a problem that electrical connection becomes incomplete during thermocompression bonding of the anisotropic conductive film 78 in a later step.

In addition, the conductive convex portion 75 formed by the electroplating method has a very small contact area with the conductive internal electrode 72, and most of it is in contact with the piezoelectric material film 71 which is a non-conductor. Since they come into contact with each other, almost no electrochemical adhesion can be obtained. Therefore, there is a problem that the conductive convex portion 75 is peeled off due to a processing resistance due to a cutting process of the sintered body 70 performed in a later step, an internal stress generated when the element is driven, or the like.

The present invention has been made in order to solve the above-mentioned problems, and cuts an element by forming a conductive convex portion having excellent electrochemical adhesion and a stable shape. To provide a laminated piezoelectric element capable of preventing peeling and adhesion failure of a conductive convex portion that occurs at the time of driving or driving, and securely connecting an internal electrode and an external electrode to prevent conduction failure and insulation failure. It is an object.

[0010]

In order to achieve this object, a laminated piezoelectric element of the present invention is a laminated piezoelectric element in which piezoelectric materials and internal electrodes are alternately laminated. Conductive protrusions formed on the end portions of the one-layer internal electrodes exposed on the side faces of the element, and continuously formed on the side faces of the multilayer piezoelectric element, and the conductive protrusions and anisotropy. An external electrode electrically connected via a conductive film, the conductive convex portion, a conductive paste layer formed by baking a conductive paste on the end of the internal electrode, and the conductive paste layer And an electroplating layer applied on top.

The conductive paste is preferably applied by screen printing.

[0012]

The laminated piezoelectric element of the present invention having the above-described structure has a conductive paste layer formed by baking a conductive paste on the ends of the internal electrodes, and a conductive paste layer formed on the conductive paste layer. Since it is composed of an electroplated layer that is applied, it has excellent electrochemical adhesion.
Moreover, it is possible to form a conductive convex portion having a stable shape.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the laminated piezoelectric element of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the laminated piezoelectric element of the present invention. On the side surface of the laminated body in which the film-shaped piezoelectric material 11 and the internal electrodes 12 are alternately laminated, the internal electrodes 12 arranged in a single layer
The conductive protrusion 16 composed of the conductive paste layer 16a and the electroplating layer 16b is formed at the end of the. Further, the insulating layer 18 is formed so as to cover all the piezoelectric materials 11 in the stacking direction of the element, and the anisotropic conductive film 13 including the conductive particles 17 is thermocompression bonded thereto. Therefore, the conductive particles 17 penetrate the insulating layer 18 and come into contact with the conductive protrusions 16, and the conductive protrusions 16 are electrically connected to the copper foil 15 serving as an external electrode through the anisotropic conductive film 13. ing.

Next, a method of manufacturing the laminated piezoelectric element shown in FIG. 1 will be described with reference to FIGS.

First, after mixing a piezoelectric material containing PZT (lead zirconate titanate) as a main component to a desired composition, 85
An appropriate amount of binder, a small amount of a plasticizer and a defoaming agent are added to the powder calcined at 0 ° C., and the powder is dispersed in an organic solvent to form a slurry. This slurry is formed into a green sheet by a doctor blade method to a predetermined thickness. A Pd (palladium) paste is screen-printed as the internal electrodes 12 on the green sheet, and a predetermined number of punched products having a predetermined size are stacked and integrated by hot pressing. After degreasing, sintering was performed at about 1200 ° C., and as shown in FIG. 2, Ag paste was used as temporary external electrodes 22 and 23 on the sintered body 21 cut at a position where the internal electrodes 12 were exposed at every other layer. A conductive paste such as the above is applied and baked, and further cut so that another pair of side surfaces 24 and 25 is exposed.

Then, on one side surface 24 of the sintered body 21, a conductive paste such as Ag, Pd, or Pt is screen-printed on the end portion of the internal electrode 12 placed in a single layer, and baked, as shown in FIG. Then, a conductive paste layer 16a firmly adhered to the piezoelectric material 11 and the internal electrode 12 is formed. Further, FIG. 4 shows a cross-sectional view of the sintered body 21 on which the conductive paste layer 16a is formed.

Here, the film thickness of the piezoelectric material 11 is 100 μm.
In the case of the degree, the width of the conductive paste layer 16a is 30-40 μm.
It is suitable to set it to about m.

Next, on one side surface 24 of the sintered body 21, the portion other than the conductive convex portions is masked with a tape. That is, the masking tape is attached to the surface on which the temporary external electrodes 22 and 23 are applied, and further the masking tape is attached to the entire other side surface 25.

Then, as shown in FIG. 5, an electroplating layer 16b is formed on the conductive paste layer 16a by electroplating. This electroplating layer 16b may be a general nickel plating. Specifically, when a nickel sulfamate bath is used as the plating bath and the temporary external electrode 22 is used as the cathode at a current density of 1 to 5 A / dm ² , it is carried out for a predetermined time. , The internal electrode 12 and the conductive paste layer 1 connected to the temporary external electrode 22
An electroplated nickel layer serving as electroplated layer 16b is formed on 6a. The electroplating layer 16b firmly adheres to the conductive paste layer 14, and is firmly connected to the piezoelectric material film 11 and the internal electrode 12, and the conductive convex portions 16 having a stable shape are formed every other layer.

Next, as shown in FIG. 6, the internal electrode 12 on which the conductive convex portion 16 is formed by the electrodeposition coating method or the like.
The internal electrode 12 on which the conductive protrusions 16 are not formed on the surface of the conductive protrusions 16 is formed by electrodepositing the resin component 41 on the end portions thereof respectively and then baking at about 150 ° C. Since 41 has fluidity in the process of hardening, it is flattened and the insulating layer 18 is formed as shown in FIG.

Further, in addition to the sintered body 21, an anisotropic conductive film 13 containing conductive particles 17 as shown in FIG. A copper foil 15 serving as an electrode is attached and prepared, and is temporarily fixed to the side surface 24 of the sintered body 21 on which the conductive convex portion 16 is formed with a length that covers the entire conductive convex portion 16. And
When sandwiched by a pair of flat pressing jigs (not shown) heated to about 120 ° C. and thermocompression bonded with a load of several kg, as shown in FIG. 1, the anisotropic conductive film 13 becomes conductive. Since only the portion facing the convex portion 16 is partially pressed with a higher pressure than the other portions, the conductive particles 17 in the portion pressed with the high pressure break through the insulating layer 18 and the conductive convex portion. Contact with 16. As a result, the copper foil 15, which is the external electrode, has the conductive projection 16 and the internal electrode 1 via the anisotropic conductive film 13.
It is electrically connected every other layer.

On the other hand, the side surface 2 on which the conductive convex portion 16 is formed
The same processing is performed on the side surface 25 on the side opposite to 4, further shifting.

In this way, the sintered body 21 in which the layers of the internal electrodes 12 and the copper foil 15 are electrically connected to each other by shifting the layers on the opposite side surfaces to each other, after being cut to a predetermined size, A lead wire for power supply is attached to a part of the copper foil 15, and a resin sheath and polarization treatment are applied to complete the product.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, chrome plating or copper plating may be used instead of nickel plating, and a conductive tape or the like may be used instead of copper foil.

[0026]

As is apparent from the above description, in the laminated piezoelectric element of the present invention, the conductive convex portion is provided on the conductive paste layer connected to the internal electrode and the conductive paste layer. Since it is composed of an electroplating layer, it is possible to form a conductive convex portion having excellent electrochemical adhesion and a stable shape, and as a result, peeling of the conductive convex portion during element processing. And adhesion failure can be prevented, and electrical connection between the internal electrode and the external electrode is ensured, and conduction failure and insulation failure can be prevented.

Further, since the conductive paste layer is applied by screen printing, the process of forming the conductive convex portion can be simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laminated piezoelectric element of this example.

FIG. 2 is a perspective view showing a part of a laminated sintered body.

FIG. 3 is a perspective view showing a part of a laminated sintered body on which a conductive paste layer is formed.

FIG. 4 is a cross-sectional view of a laminated sintered body on which a conductive paste layer is formed.

FIG. 5 is a diagram showing a process of forming an electroplating layer on a conductive paste layer.

FIG. 6 is a diagram showing a step of electrodepositing a resin component to be an insulating layer on a laminated sintered body on which conductive protrusions are formed.

FIG. 7 is a diagram showing a step of forming an insulating layer on the laminated sintered body on which the conductive protrusions are formed.

FIG. 8 is a diagram showing a state in which an anisotropic conductive film and a copper foil to be an external electrode are attached.

FIG. 9 is a diagram showing a manufacturing process of a conventional laminated piezoelectric element.

FIG. 10 is a diagram showing a manufacturing process of a conventional laminated piezoelectric element.

[Explanation of symbols]

 Reference Signs List 11 piezoelectric material film 12 internal electrode 13 anisotropic conductive film 15 copper foil (external electrode) 16 conductive protrusion 16a conductive paste layer 16b electroplating layer

Claims (2)

[Claims] 1. A laminated piezoelectric element in which a piezoelectric material and internal electrodes are alternately laminated, and a conductive material formed at an end portion of each one-layer internal electrode exposed on a side surface of the laminated piezoelectric element. A protrusion and an external electrode that is continuously formed on the side surface of the multilayer piezoelectric element and that is electrically connected to the conductive protrusion through an anisotropic conductive film. A laminated piezoelectric material characterized in that the convex portion is composed of a conductive paste layer formed by baking a conductive paste on the end of the internal electrode, and an electroplating layer applied on the conductive paste layer. element. 2. The laminated piezoelectric element according to claim 1, wherein the conductive paste is applied by screen printing.